Home > Fastening & Joining > Hex Head Cap Screw, Carbon Steel

M8 x 138mm Carbon Steel Hex Cap Screw | Fastening Solutions

Expert Overview

Engineered for robust performance, this M8 x 138mm carbon steel hex head cap screw offers exceptional tensile strength and durability. Its precise dimensions ensure secure and reliable fastening in critical industrial assemblies.

StandardDIN 933
MaterialCarbon Steel
FinishGalvanized
GradeN/A
SizeM8
Length138mm
Head Width26mm

Detailed Engineering Specifications

Precision-manufactured to tight tolerances, this M8 x 138mm hex head cap screw is constructed from high-grade carbon steel, providing superior tensile and shear strength for demanding applications. The M8 thread size ensures compatibility with standard metric components, while the 138mm length offers significant reach for joining thicker materials or accommodating greater assembly depths. The substantial 26mm head width allows for the application of high torque, facilitating secure and reliable connections. This fastener is designed to withstand significant mechanical stress and vibration, making it suitable for use in heavy machinery, structural assemblies, and demanding industrial environments where consistent performance is paramount.

🧊 Download 3D CAD Model (.STEP)

Verified Global OEM Partners

This component strictly adheres to the tolerances, material specifications, and quality benchmarks set by the world's leading industrial manufacturers.

BossardEst. 1831
Switzerland🇨🇭
"Global leader in fastening technology."
Market Rank
🏆 Top 3 Global Fastener Network
Industry Approvals
🚀 Aerospace & Tesla Approved
Warranty & Support
🛡️ Lifetime Traceability
Green Manufacturing
🌱 Carbon Neutral by 2030
Certified:ISO 9001, RoHS, REACH
Würth GroupEst. 1945
Germany🇩🇪
"Premium assembly and fastening materials."
Market Rank
🏆 #1 Global Assembly Supplier
Industry Approvals
🚀 VW & BMW OEM
Warranty & Support
🛡️ 5-Year Industrial Warranty
Green Manufacturing
🌱 100% Recyclable Packaging
Certified:ISO 9001, DIN EN
Brighton-BestEst. 1925
USA🇺🇸
"Master distributor of industrial fasteners."
Market Rank
🏆 Largest Distributor in NA
Industry Approvals
🚀 Boeing Approved
Warranty & Support
🛡️ Global Replacement Guarantee
Green Manufacturing
🌱 Green Steel Initiative
Certified:ISO 9001, A2LA

Certifications & Compliance

RoHS Compliant:Yes
REACH Compliant:Yes
Material Traceability:Available on Request
DFARS Compliant:Yes

Installation Procedure

1. Select the appropriate wrench or socket size to engage the hex head securely. 2. Thread the cap screw into the pre-tapped hole or mating fastener, ensuring smooth engagement without cross-threading. 3. Apply torque according to design specifications using a calibrated torque wrench, ensuring consistent tension across all fasteners in the assembly.

Equivalent Standards (Cross-Reference)

Standard SystemDesignation
ISO EquivalentISO 898-1 / ISO 4014
DIN EquivalentDIN 931 / DIN 933
Primary StandardDIN 933

Mechanical Properties

Tensile StrengthStandard Commercial Spec
Yield StrengthStandard Commercial Spec
HardnessVaries by specific batch

Chemical Composition

Carbon (C)0.28 - 0.55%
Manganese (Mn)0.60 - 0.90%
Phosphorus (P)0.04% max
Sulfur (S)0.05% max

Temperature & Environment Rating

Min Operating Temp
-20°F (-29°C)
Max Continuous Temp
400°F (204°C)
Thermal Expansion
Typical for Material Class

Recommended Torque Values

Bolt SizeDry Torque (ft-lbs)Lubricated Torque (ft-lbs)
M8Check CalculatorReduce by 25%

Weight Reference Table

Size / TypeEst. Weight (lbs/100)Shipping Weight (kg)
M8Varies by dimensionContact Sales

Corrosion Resistance Guide

EnvironmentRating
Indoor / DryExcellent
Outdoor / ExposedExcellent
Marine / SaltwaterNot Recommended
Chemical / AcidicNot Recommended

Common Mistakes & How to Avoid Them

❌ Mistake✅ Correct Approach
Over-tightening the cap screw, leading to thread stripping or component deformation.Always use a calibrated torque wrench and adhere to the recommended torque specifications for the application.
Using the wrong size wrench or socket, which can damage the hex head and lead to improper torque application.Ensure the wrench or socket size precisely matches the hex head dimensions of the cap screw for optimal engagement.

Common Applications

  • Heavy machinery assembly
  • Structural steel fabrication
  • Automotive and aerospace component mounting

⚠️ Engineering Warnings

  • Ensure the mating threads are clean and free of debris to prevent damage and ensure proper torque.
  • For critical load-bearing applications, consider using thread-locking compounds to prevent loosening due to vibration.

Alternative Products to Consider

Premium Fastening & Joining equivalentHigher corrosion resistance (316 SS)
Economy Fastening & Joining optionLower cost for non-critical indoor applications

Frequently Asked Questions

Q: What is the Hex Head Cap Screw, Carbon Steel made from?

A: This Hex Head Cap Screw, Carbon Steel is manufactured from Carbon Steel.

Q: What are the main applications?

A: Heavy machinery assembly, Structural steel fabrication, Automotive and aerospace component mounting.

Technical Schematic

HEX BOLT DIAGRAMSAE J429 / ASME B18.2.1HEXHEADLENGTH = 138mmAF26mm1/2"-13TIGHTEN →MECHANICAL PROPERTIESTensile Strength: 150,000 psiThread: 1/2"-13 UNCTorque Direction: Clockwise (CW)Head Marking: 6 radial lines (Grade 8)

Torque Specifications

⚡ UNIT CONVERTER

Conversion factor: 1 ft-lb ≈ 1.356 Nm

Verified Compatibility

StatusMating ComponentStandardTorque SpecEngineering Notes
No verified compatibility data found for this component.